ELECTRONIC-DRIVING TYPE CONTINUOUS VARIABLE SHUTTER SYSTEM

PURPOSE: To recognize the position of electronically driven shutter blades to precisely control the aperture size and the exposure time by constituting the shutter blades so that they can form plural aperture holes accompanied with plural exposure times. CONSTITUTION: The current quantity inputted to a coil 13 determines a magnetic flux between pole chips 14 and 15. This magnetic flux generates torque on a magnet 16, and as the result, an arm 18 is rotated counterclockwise. It is necessary only that the relation between this current and the angle of rotation is approximately linear. Thus, the position of the magnet 16 can be successively changed, and shutter blades 27 to 29 can form many different aperture holes. A Ball effect sensor 21 is arranged very closely to the magnet 16 and measures a magnetic field of the boundary generated by the magnet 16. The sensor 21 is fixed and stopped though the magnet 16 is rotated, and the sensor 21 measures the change of the density of the magnetic flux generated by the magnet 16.